Reference Guide

Layer 2 | 547
Important Points about Configuring Redundant Pairs
• You may not configure any interface to be a backup for more than one interface, no interface can have
more than one backup, and a backup interface may not have a backup interface.
• Neither the active nor the backup interface may be a member of a LAG.
• The active and standby do not have to be of the same type (1G, 10G, etc).
• You may not enable any Layer 2 protocol on any interface of a redundant pair or to ports connected to
them.
In Figure 27-4, interface 3/41 is a backup interface for 3/42, and 3/42 is in the down state, as shown in
message Message 1. If 3/41 fails, 3/42 transitions to the up state, which makes the backup link active. A
message similar to Message 1 appears whenever you configure a backup port.
Figure 27-4. CLI for Configuring Redundant Layer 2 Pairs without Spanning Tree
Message 1 Configuring a Backup Layer 2 Port
02:28:04: %STKUNIT0-M:CP %IFMGR-5-L2BKUP_WARN: Do not run any Layer2 protocols on Te
3/41 and Te 3/42
02:28:04: %STKUNIT0-M:CP %IFMGR-5-OSTATE_DN: Changed interface state to down: Te 3/42
02:28:04: %STKUNIT0-M:CP %IFMGR-5-STATE_ACT_STBY: Changed interface state to standby:
Te 3/42
FTOS(conf-if-range-te-3/41-42)#switchport backup interface TenGigabitEthernet 3/42
FTOS(conf-if-range-te-3/41-42)#show config
!
interface TenGigabitEthernet 3/41
no ip address
switchport
switchport backup interface TenGigabitEthernet 3/42
no shutdown
!
interface TenGigabitEthernet 3/42
no ip address
switchport
no shutdown
FTOS(conf-if-range-te-3/41-42)#
FTOS(conf-if-range-te-3/41-42)#do show ip int brief | find 3/41
TenGigabitEthernet 3/41 unassigned YES Manual up up
TenGigabitEthernet 3/42 unassigned NO Manual up down
[output omitted]
FTOS(conf-if-range-te-3/41-42)#interface tengig 3/41
FTOS(conf-if-te-3/41)#shutdown
00:24:53: %STKUNIT0-M:CP %IFMGR-5-ASTATE_DN: Changed interface Admin state to down: Te 3/41
FTOS(conf-if-te-3/41)#00:24:55: %STKUNIT0-M:CP %IFMGR-5-OSTATE_DN: Changed interface state to
down: Te 3/41
00:24:55: %STKUNIT0-M:CP %IFMGR-5-INACTIVE: Changed Vlan interface state to inactive: Vl 1
00:24:55: %STKUNIT0-M:CP %IFMGR-5-OSTATE_UP: Changed interface state to up: Te 3/42
00:24:55: %STKUNIT0-M:CP %IFMGR-5-ACTIVE: Changed Vlan interface state to active: Vl 1
00:24:55: %STKUNIT0-M:CP %IFMGR-5-STATE_STBY_ACT: Changed interface state from standby to
active: Te 3/42
FTOS(conf-if-te-3/41)#do show ip int brief | find 3/41
TenGigabitEthernet 3/41 unassigned NO Manual administratively down down
TenGigabitEthernet 3/42 unassigned YES Manual up up
[output omitted]